Preparation, structure, and properties of styrene-ethylene-butylene-styrene block copolymer/clay nanocomposites: Part II fracture behaviors

Styrene-ethylene-butylene-styrene block copolymer (SEBS)/clay nanocomposites were prepared via a melt mixing technique. Various amounts of two types of maleated compatibilizers, styrene-ethylene-butylene-styrene block copolymer grafted maleic anhydride (SEBS-g-MA) and polypropylene grafted maleic anhydride (PP-g-MA), were incorporated to improve the dispersion of commercial organoclay (denoted as 20A), respectively. PP-g-MA compatibilized system conferred higher tensile strength and tear strength (initiation condition) than SEBS-g-MA compatibilized system. At a fixed content of compatibilizers, the above mechanical properties were improved with increasing clay content as well. By relating tensile strength to tear strength (arrest condition), the average depth of flaw was in the range of 33.8 ± 3.4 μm, which successfully confirmed the extension of Rivlin and Thomas’s theory for conventional elastomers to thermoplastic elastomer/clay nanocomposites for the first time. Cutting strength of SEBS/clay nanocomposites gave an intermediate value when compared with crystalline plastics and conventional amorphous elastomers, which further signified the importance of micro-yielding of styrene domains, crystalline yielding of compatibilizer, and filler reinforcement even in the nano-fracture zone of deformation.     

Preparation and properties of isobutylene–isoprene rubber–clay nanocomposites

Isobutylene isoprene rubber (IIR)‐clay nanocomposites have been prepared successfully by melt intercalation with maleic anhydride‐grafted IIR (Ma‐g‐IIR) and organophilic clay. In IIR‐clay nanocomposites, the silicate layers of the clay were exfoliated and dispersed into the monolayer. The nanocomposites exhibited greater gas barrier properties compared with those of Ma‐g‐IIR. When 15 phr clay was added, gas barrier properties were 2.5 times greater than those of Ma‐g‐IIR. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1182–1188, 2006     

Polyolefin-functionalized graphene oxide and its GO/HDPE nanocomposite with excellent mechanical properties

An effective strategy for the polyolefin-functionalized graphene oxide (fGO) using two-step methods has been reported for GO/HDPE nanocomposite with excellent mechanical properties.     

Studies of ABS-graft-maleic anhydride/clay nanocomposites: Morphologies, thermal stability and flammability properties

ABS-g-MAH (maleic anhydride) with different grafting degree, ABS/OMT (organo montmorillonite) and ABS-g-MAH/OMT nanocomposites were prepared via melt blending. The grafting reaction, phase morphology, clay dispersion, thermal properties, dynamic mechanical properties and flammability properties were investigated. FTIR spectra results indicate that maleic anhydride was successfully grafted onto butadiene chains of the ABS backbone in the molten state using dicumyl peroxide as the initiator and styrene as the comonomer and the relative grafting degree increased with increasing loading of MAH. TEM images show the size of the dispersed rubber domains of ABS-g-MAH increased and the dispersion is more uniform than that of neat ABS resin. XRD and TEM results show that intercalated/exfoliated structure formed in ABS-g-MAH/OMT nanocomposites and the rubber phase intercalated into clay layers distributed in both SAN phase and rubber phase. TGA results reveal the intercalated/exfoliated structure of ABS-g-MAH/OMT nanocomposites has better barrier properties and thermal stability than intercalated ones of ABS/OMT nanocomposites. The T_g of ABS-g-MAH/OMT nanocomposites was also higher than that of neat ABS/OMT nanocomposites. The results of cone measurements show that ABS-g-MAH/OMT nanocomposites exhibit significantly reduced flammability when compared to ABS/OMT nanocomposites even at the same clay content. The chars of ABS-g-MAH/OMT nanocomposites were tighter, denser, more integrated and fewer surface microcracks than ABS/OMT residues.     

Radiation Crosslinking of Chlorinated Poly(Isobutylene-co-Isoprene) with Polyfunctional Monomers

Abstract

It is well known that poly(isobutylene-co-isoprene) (butyl rubber, IIR) is degraded by irradiation. However, we demonstrated that IIR, after chlorination (CIIR) crosslinks by electron beam (EB) irradiation. The gel dose for CIIR was 3.8 kGy. To avoid scission of the main chain, various polyfunctional monomers were added for crosslinking of CIIR at lower doses. It was found that trimethylolpropane trimethacrylate (TMPT) is the most effective accelerator for crosslinking of CIIR at a lower dose. The tensile strength of EB crosslinked by CIIR increases almost linearly with increasing TMPT content.     

Nanotailoring of sepiolite clay with poly [styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene]: structure–property correlation

Poly [styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS)/sepiolite clay nanocomposites are prepared by solvent casting method. Two types of schemes have been adopted to establish the compatibility between nonpolar polymer (SEBS) and needle‐like inorganic filler (sepiolite), either by polar modification of the nonpolar polymer or organic modification of the inorganic filler. Structure–property correlation of nanocomposites derived from two different approaches is compared. Structural and morphological analysis of nanocomposites has been investigated by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. Fourier transform infrared result shows better compatibility between SEBS and modified sepiolite clay compared to maleic anhydride grafted SEBS and pristine sepiolite in their nanocomposites. Tensile strength and % elongation are found to increase by 32 and 105%, respectively, with the addition of just 3 parts per hundred parts of resin (phr) modified sepiolite clay to pristine SEBS matrix. Moreover, thermal stability has also improved by 96°C with similar loading. This work provides a new insight into the structure and thermo‐mechanical properties of novel SEBS–sepiolite clay nanocomposites. Copyright © 2017 John Wiley & Sons, Ltd.     

Polystyrene nanocomposites based on an oligomerically-modified clay containing maleic anhydride

An oligomerically-modified clay containing maleic anhydride was used to prepare polystyrene-clay nanocomposites by melt blending and the effect of this modified clay on the thermal stability and fire performance was studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed immiscible/intercalated/delaminated morphology. The maleic anhydride modified clay improved the compatibility between the clay and the polystyrene.     

Preparation and characterization of PE and PE-g-MAH/montmorillonite nanocomposites

Polyethylene (PE) was chemically modified with grafting maleic anhydride (MAH) monomer on its backbone at first. Then the melt-direct intercalation method was employed to prepare two kinds of nanocomposites, polyethylene (PE)/organic montmorillonite (Org-MMT) and maleic anhydride grafted polyethylene (PE-g-MAH)/Org-MMT nanocomposites. X-ray diffractometery (XRD) was used to investigate the intercalation effect and transmission electron microscopy (TEM) to observe the dispersion of Org-MMT interlayers in matrixes. The results show that an intercalated structure would be acquired on mixing the PE and Org-MMT; and an almost exfoliated system would be obtained by mixing the PE-g-MAH and Org-MMT. Moreover, further measurements via thermogravimetric (TGA) and differential scanning calorimetry (DSC) showed that both of the nanocomposites had a higher thermal decomposition temperature and a higher crystallization temperature when compared to the original matrix. At the same time, the thermal and crystal properties for the PE-g-MAH prepared in this experiment are also discussed.     

Toughening Poly(lactic acid) with Imidazolium-based Elastomeric Ionomers

Imidazolium-based elastomeric ionomers (i-BIIR) were facilely synthesized by ionically modified brominated poly(isobutylene-co-isoprene) (BIIR) with different alkyl chain imidazole and thoroughly explored as novel toughening agents for poly(lactic acid) (PLA). The miscibility, thermal behavior, phase morphology and mechanical property of ionomers and blends were investigated through dynamic mechanical analyses (DMA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile and impact testing. DMA and SEM results showed that better compatibility between the PLA and i-BIIR was achieved compared to the PLA/unmodified BIIR elastomer. A remarkable improvement in ductility with an optimum elongation at break up to 235% was achieved for the PLA/i-BIIR blends with 1-dodecylimidazole alkyl chain (i-BIIR-12), more than 10 times higher than that of pure PLA. The impact strengths of PLA were enhanced from 1.9 kJ/m² to 4.1 kJ/m² for the PLA/10 wt% i-BIIR-12 blend. Toughening mechanism had been established by systematical analysis of the compatibility, intermolecular interaction and phase structures of the blends. Interfacial cavitations initiated massive shear yielding of the PLA matrix owing to a suitable interfacial adhesion which played a key role in the enormous toughening effect in these blends. We believed that introducing imidazolium group into the BIIR elastomer was vital for the formation of a suitable interfacial adhesion.     

Design,Synthesis and Characterization of 3,4-Dihydro-2H-pyran Containing Copolymer/Clay Nanocomposites

We introduce briefly surface modification of clay minerals, structure, properties and, characterization techniques of polymer-clay (PCN's) nanocomposites. Organically modified layered-silicates or nanoclays have become an attractive class of hybrid materials due to their prospective use in a great variety of applications from industry to health. For design, synthesis and characterization for potential biomedical nanocomposites, antitumor-active copolymer; poly(DHP-alt-MA) were used to prepare copolymer/clay nanocomposites. The functional copolymers, having a combination of rigid/flexible linkages and an ability of complex-formation with interlayered surface of organo-silicate, and their nanocomposites have been synthesized by interlamellar complex-radical copolymerization of intercalated monomer complexes of maleic anhydride (MA) and 3,4-Dihydro-2H-pyran (DHP) with three alkyl ammonium salts surface modified bentonite and monomer mixtures. Poly(DHP-alt-MA) pristine copolymer and poly(DHP-alt-MA)/organically modified bentonite nanocomposites were characterized by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), HR-Raman, X-ray diffraction (XRD) and TEM methods.     

Carboxylate clays: A model study for polypropylene/clay nanocomposites

Sodium-montmorillonite was intercalated by carboxylate salts to prepare carboxylate clays. The intercalation of sodium acetate doubles the clay basal spacing and no degradation of the carboxylate clay is noticed in the extrusion temperature range. These carboxylate clays were used to synthesize polypropylene-graft-maleic anhydride (PP-g-MA)/clay nanocomposites. Nanocomposites were also produced by a one-pot process using in situ prepared carboxylate clay. The carboxylate salts within the clay layers partially neutralize the maleic anhydride groups of the PP-g-MA matrix, in situ during the melt compounding. The ionic groups of the partially neutralized polymer offer favourable interactions with the clay, hence reinforcing the interfacial bond between the polymer and the clay and improving the composite properties. The use of carboxylate clay clearly improves the clay dispersion into the PP-g-MA matrix and improves the nanocomposite’s thermal and rheological properties.     

Extruder‐made TPO nanocomposites. II. Effect of maleated poly(propylene)/organoclay ratio on morphology and thermal expansion behavior

Coefficients of linear thermal expansion (CTE) for poly(propylene)/ poly(propylene)‐grafted‐maleic anhydride/montmorillonite ethylene‐co‐octene elastomer (PP/PP‐g‐MA/MMT/EOR) blend nanocomposites were determined as a function of MMT content and various PP‐g‐MA/organoclay masterbatch ratios. The nanocomposites were prepared in a twin‐screw extruder at a fixed 30 wt % elastomer, 0–7 wt % MMT content, and various PP‐g‐MA/organoclay ratio of 0, 0.5, 1.0, and 1.5. The organoclay dispersion facilitated by the maleated PP helps to reduce the size of the dispersed phase elastomer particles in the PP matrix. The elastomer particle size decreased significantly as the PP‐g‐MA/organoclay ratio and MMT content increased; the elastomer particles viewed // to flow direction (FD) are smaller and less deformed compared to those viewed // to transverse direction (TD). The elastomer particle shape based on the view along the three orthogonal directions of the injection molded sample is similar to a prolate ellipsoid. The CTE decreased significantly in the FD and TD, whereas a slight increase is observed in the normal direction in the presence of MMT and PP‐g‐MA. The Chow model based on a two population approach showed better fit to experimental CTE when the effect of MMT and elastomer are considered individually. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B Polym. Phys. 2013 , 51, 952–965     

Toughening of ethylene-propylene random copolymer/clay nanocomposites: Comparison of different compatibilizers

Ethylene/propylene-random-copolymer(PPR)/clay nanocomposites were prepared by two-stage melt blending. Four types of compatibilizers,including an ethylene-octene copolymer grafted maleic anhydride(POE-g-MA) and three maleic-anhydride-grafted polypropylenes(PP-g-MA) with different melt flow indexes(MFI),were used to improve the dispersion of organic clay in matrix.On the other hand,the effects of organic montmorillonite(OMMT) content on the nanocomposite structure in terms of clay dispersion in PPR matrix,thermal behavior and tensile properties were also studied. The X-ray diffraction(XRD) and transmission electron microscopy(TEM) results show that the organic clay layers are mainly intercalated and partially exfoliated in the nanocomposites.Moreover,a PP-g-MA compatibilizer(compatibilizer B) having high MFI can greatly increase the interlayer spacing of the clay as compared with other compatibilizers.With the introduction of compatibilizer D(POE-g-MA),most of the clays are dispersed into the POE phase,and the shape of the dispersed OMMT appears elliptic,which differs from the strip of PP-g-MA.Compared with virgin PPR,the Young’s modulus of the nanocomposite evidently increases when a compatibilizer C(PP-g-MA) with medium MFI is used.For the nanocomposites with compatibilizer B and C,their crystallinities(X_c) increase as compared with that of the virgin PPR. Furthermore,the increase of OMMT loadings presents little effect on the melt temperature(T_m) of the PPR/OMMT nanocomposites,and slight effect on their crystallization temperature(T_c).Only compatibilizer B can lead to a marked increases in crystallinity and T_c of the nanocomposite when the OMMT content is 2 wt%.     

尼龙6/(乙烯-辛烯)共聚物弹性体的流变及结晶行为

（乙烯 辛烯）共聚物弹性体（ＰＯＥ）是由美国ＤＯＷ化学公司使用茂金属催化剂聚合而成的一种聚烯烃橡胶．与传统聚烯烃类橡胶ＥＰＤＭ相比,ＰＯＥ的特点就在于其在聚烯烃塑料基体中分散速度快、分散程度高．为此,我们尝试用马来酸酐接枝的ＰＯＥ（ＰＯＥ ｇ ＭＡ）...     

Compatibilized polyethylene—thermally reduced graphene nanocomposites: Interfacial interactions and hyperspectral mapping for component distribution

Ethylene-co-acrylic acid (EAA) and ethylene-co-methacrylic acid ionomer (EMAZ) copolymers were used as compatibilizers for polyethylene-graphene nanocomposites generated by melt mixing. At 5 wt% content, the EAA compatibilizer enhanced the tensile modulus of PE by 40 % and shear modulus by >300 % (1 rad/s) due to efficient dispersion of graphene platelets which helped in effective stress transfer. These also resulted in enhanced thermal stability for PE-EAA-G nanocomposite as compared to nanocomposite with EMAZ. The properties of the nanocomposites were significantly better than the conventional nanocomposites based on layered silicate materials. Mapping of the component distribution in the nanocomposites was demonstrated by using hyperspectral imaging. The nanocomposite with EAA exhibited higher extent of spectral signal mixing due to better mixing of filler and compatibilizer in PE matrix. On the other hand, nanocomposite with EMAZ had no spectral mixing as the components did not mix optimally with each other. The DSC thermogram for this nanocomposite also exhibited a small shoulder at low temperature probably due to immiscibility of the compatibilizer with the matrix polymer. The hyperspectral imaging and mapping was thus demonstrated to be a useful method for determination of component distribution in complex nanocomposite systems.     

Preparations and properties of waterborne polyurethane/allyl isocyanated-modified graphene oxide nanocomposites

We synthesized waterborne polyurethane (WPU)/allyl isocyanate modified graphene oxide (iGO) nanocomposites by UV curing, and the effects of iGO on the mechanical, dynamic mechanical, and thermal properties of the nanocomposites were systematically investigated. It was shown that the iGO chemically incorporated into the WPU chains by covalent bonding acts as a multifunctional cross-linking agent as well as reinforcing filler. Consequently, the tensile strength, glassy and rubbery state moduli, glass transition temperature, and thermal stability of the WPU were significantly increased up to an iGO content of 1%, beyond which most of the above properties showed a decrease, due probably to the auto-inhibition of the allyl compounds.     

Preparation of polypropylene/sepiolite nanocomposites using supercritical CO2 assisted mixing

Well dispersed polypropylene (PP)/sepiolite clay nanocomposites were prepared successfully using supercritical carbon dioxide (scCO₂) assisted mixing with and without the presence of maleic anhydride grafted polypropylene (PP-g-MA) as compatibilizer. The resulting morphology and polymorphism of nanocomposites were established using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations. The mechanical properties of the nanocomposites were investigated and compared with those obtained by a traditional melt compounding method. Our results showed that by using scCO₂ in the process, we were able to obtain better sepiolite dispersions and reduce breakage of sepiolite fibres. Consequently, a significant improvement in the yield stress was observed for the nanocomposites processed in scCO₂ compared to those processed by the traditional melt compounding. XRD data also indicated that the resulting nanocomposites had only α-phase crystallites of PP while the presence of sepiolite could also induce preferred orientation of these α-phase crystallites.     

Fire properties of styrenic polymer-clay nanocomposites based on an oligomerically-modified clay

An oligomerically-modified clay has been used to fabricate nanocomposites with styrenic polymers, such as polystyrene, high-impacted polystyrene, poly(styrene-co-acrylonitrile) and acrylonitrile-butadiene-styrene by melt blending. The clay dispersion was evaluated by X-ray diffraction and bright field transmission electron microscopy. All of the nanocomposites have a mixed delaminated/intercalated structure. The fire properties of nanocomposites were evaluated by cone calorimetry a nd the mechanical properties were also evaluated.     

Effect of the C/O ratio in graphene oxide materials on the reinforcement of epoxy-based nanocomposites

The effect of the C/O ratio of graphene oxide materials on the reinforcement and rheological percolation of epoxy-based nanocomposites has been studied. As-prepared graphene oxide (GO) and thermally-reduced graphene oxide (TRGO) with higher C/O ratios were incorporated into an epoxy resin matrix at loadings from 0.5 to 5 wt %. Tensile testing revealed good reinforcement of the polymer up to optimal loadings of 1 wt %, whereas agglomeration of the flakes at higher loadings caused the mechanical properties of the composites to deteriorate. The level of reduction (C/O) of the graphene oxide filler was found to influence the mechanical and rheological properties of the epoxy composites. Higher oxygen contents were found to lead to stronger interfaces between graphene and epoxy, giving rise to higher effective Young's moduli of the filler and thus to superior mechanical properties of the composite. The effective modulus of the GO in the nanocomposites was found to be up to 170 GPa. Furthermore, rheological analysis showed that highly oxidized graphene flakes did not raise the viscosity of the epoxy resin significantly, facilitating the processing considerably, of great importance for the development of these functional polymeric materials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 281–291     

Some novel layered-silicate nanocomposites based on a biodegradable hydroxybutyrate copolymer

This paper describes the preparation, characterization, mechanical properties and thermal stability of layered silicate nanocomposites based on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-co-PHH, known as Nodax^TM). The dispersed phases were organically modified montmorillonites (clay 20A and clay 25A), mica, and talc, and they were introduced by solution mixing. Wide-angle X-ray scattering results and transmission electron microscopy (TEM) images confirmed that these two clays were intercalated and finely distributed in the Nodax^TM matrix. This type of layered filler led to remarkable improvements in mechanical properties even at very low loadings. Minimizing aggregation was more of a problem in the case of the mica and the talc, at least in this particular matrix. In some cases, these layered fillers slightly decreased the thermal stability of the Nodax^TM.